1. Technical Field of the Invention
The present invention relates to self-sealing, tamper-evident closures for use on containers, and methods for making same. More particularly, the present invention relates to tamper-evident closures having an integrally-formed self-sealing valve cured in place.
2. Discussion of the Prior Art
Closures having a self-sealing dispensing orifice are relatively well-known in the prior art. Typically, such closures include a flexible gasket valve and a separate cap body. Generally, the complete closure assembly is formed through a multiple-step process comprising the steps of forming a flexible gasket from a rubber material such as silicone; punching a longitudinal slit through the flexible gasket to allow a liquid to pass therethrough; forming a hard, plastic cap body to support and hold the flexible gasket in place; and, and placing the flexible gasket in the cap body. The complete closure assembly is then threadingly attached to the open neck of a container, which cooperates with the threads of the cap body to retain the flexible gasket and hold it firmly in place.
Dispensing of a liquid contained within the container is achieved by increasing the pressure therein, such as by squeezing the sides of the container. The build-up of pressure behind the flexible gasket forces the longitudinal slit to open, permitting liquid to pass therethrough. Upon releasing the applied pressure, the slit returns to its original "closed" position, thereby sealing the container against further dispensing.
U.S. Pat. No. 4,991,745 to Brown is typical of prior art self-sealing closures comprising a separate gasket valve and cap. However, a gasket valve which is separate and removable from the cap body may disassociate itself from the cap body, falling within the container or otherwise becoming lost, thereby rendering the closure ineffective to both seal the container and provide a recloseable dispensing means. Further, additional manufacturing steps are required to separately form the several component parts and then assemble all parts together requires expensive equipment and production time.
Attempts have been made to provide a closure with an integral, self-sealing gasket. U.S. Pat. No. 4,201,491 to Kohler is an example of a one-piece, single-composition rubber closure having a dispensing slit. However, such one-piece rubber closures do not possess the rigidity necessary to provide a closure which is difficult to remove from the neck of a container. And, it is desirable for a closure to possess both the rigidity of construction to prohibit the removal thereof from the neck of a container, while furthermore possessing a flexible member to provide a self-sealing dispensing orifice.